html4和html5区别之如何在一个input上添加焦点实现

<form>
<p><label>Username:<input name=search type="text" id="search"></label></p>
<script type="text/javascript">
document.getElementById ('search').focus()
</script>
</form>

<form>
<p>
<label>Search:<input name=search autofocus></label>
</p>
</form>